How can I model this problem of delivering assets by choosing a route with reinforcement learning?
I do not see how you came to choose prices as actions. Normally, actions are something like go left, go right, jump, stay etc.
Analogously, I would say that in your case the actions are visiting a certain location, whereas locations are what you referred to as states. I'd go for something like that:
locations = {location1=(c1,cr1), location2=(c1,cr2), ...}
Actions = {Visit location1, Visit location2, ...}
States = {--set of all the possible paths the model can generate until the budget is possibly exhausted--}

The reward function could then be a combination of both the acceptance (vs. rejection) of a route/path by the user and the inverse of the cost associated with the suggested path (because you want the model to favor cheap paths in order to keep your own business costs low).
How you balance these two terms is up to exploration.
For rapid prototyping, check out stable baselines, which offers a bunch of highly optimized RL algorithms.